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Homework Help: Work Problem (Chin Ups)

  1. Nov 6, 2009 #1
    1. The problem statement, all variables and given/known data

    While doing a chin-up, a man lifts his body 0.40 m.

    2. Relevant equations

    Us = mgh
    W = Fd

    a) How much work must the man do per kilogram of body mass?

    b)The muscles involved in doing a chin-up can generate about 70 J of work per kilogram of muscle mass. If the man can just barely do a 0.40-m chin-up, what percentage of his body's mass do these muscles constitute? (For comparison, the total percentage of muscle in a typical 70-kg man with 14% body fat is about 43%.)

    c)Repeat part (b) for the man's young son, who has arms half as long as his father's but whose muscles can also generate 70 J of work per kilogram of muscle mass.

    I have no clue how to begin. It seems they only provided me with [tex]\Delta[/tex]X = .40m
  2. jcsd
  3. Nov 6, 2009 #2


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    Science Advisor
    Homework Helper

    Hi Chandasouk! :smile:

    (have a delta: ∆ :wink:)
    Yes, they have … they've also provided you with the mass (because everything is per kilogram). :wink:
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